Here's another example. If a person owns apartments that are rented out at a profit, they earn money each month without working a specific number of hours. If the owner earns $100/month net income from each apartment, the determining factor is how many apartments they own, not how many hours they work. Therefore, they may own 1 apartment and make $100 net income each month, or they could own 500 apartments and make $50,000 ($100 per apartment) each month.
Residual income is the amount of net income generated in excess of the minimum rate of return. Residual income concepts have been used in a number of contexts, including as a measurement of internal corporate performance whereby a company's management team evaluates the return generated relative to the company's minimum required return. Alternatively, in personal finance, residual income is the level of income that an individual has after the deduction of all personal debts and expenses have been paid.